Rhythmic Production of CO2 by Tropical Orchid Flowers

Circadian rhythm of CO2 production was observed in some tropical orchid flowers. The tight bud showed relatively low respiration and no rhythmic changes. As soon as the flower opened, respiration increased and rhythmicity became apparent. The period for the rhythm was about 24 hours. Dark treatment and detachment dampened the amplitude of the rhythm without affecting the rhythmicity. In depollinated and pollinated flowers, the rhythmicity was less pronounced. Pollination and depollination appeared to stimulate respiration at the trough of the cycle. However, there was no significant difference in respiration per day between the untreated and treated flower. Both pollination and depollination hasten the senescence of orchid flowers.